mineral
Quartz Geode
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale. Color: White, clear, with minor yellowish or brownish iron-oxide staining. Luster: Vitreous (glassy) to greasy. Crystal structure: Trigonal. Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous (glassy) to greasy
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Physical properties
Hardness: 7 on Mohs scale. Color: White, clear, with minor yellowish or brownish iron-oxide staining. Luster: Vitreous (glassy) to greasy. Crystal structure: Trigonal. Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.65
Formation & geological history
Formed in hollow cavities in sedimentary or volcanic rocks where silica-rich groundwater or hydrothermal fluids slowly precipitate quartz crystals inward from the cavity walls over long periods.
Uses & applications
Used in decorative items, mineral collections, jewelry making, and industrial applications requiring pure silica.
Geological facts
Geodes appear as ordinary, somewhat bumpy rocks on the outside, but cracking them open reveals a sparkling interior of quartz or other mineral crystals. They are found worldwide in various geological formations.
Field identification & locations
Easily identified by its hard quartz crystals lining a hollow or central cavity, and its lack of cleavage with a conchoidal fracture. Found in regions with significant limestone, volcanic ash beds, or hydrothermal activity.
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